DE10230958A1 - Fuel injection system, for an IC motor using LPG fuel, has an additional fuel pump in the fuel line to the injection pump to increase the fuel pressure in the flow from the tank - Google Patents

Abstract

The fuel injection system (10), for an internal combustion motor, has an injection pump (14) and a tank (20) to hold the fuel which is at a medium pressure level with a vapor pressure higher than atmospheric pressure, as liquefied petroleum gas (LPG). The pressure in the tank is at a higher level than the fuel vapor pressure. A fuel pump (24) within the tank feeds the fuel to the injection pump. A second fuel pump (30) is in the fuel line (22) to the injection pump, outside the tank and downstream of the first fuel pump, to increase the fuel pressure.

Description

State of the art

The invention describes a direct fuel injection system, in particular common rail direct injection system for direct injection of liquid gas (LPG) or other spark ignited, liquid Fuels in the combustion chamber of an internal combustion engine.

Liquefied petroleum gas, also LPG (Liquified Petroleum Gas) or called LPG, is a propane-butane mixture from region to region different mixture proportions due to storage under relatively little overpressure (approx. 7 bar at room temperature) in liquid form in the fuel tank is present (for this reason also referred to here as "medium pressure fuel", in delimitation to fuels that are liquid at room temperature and atmospheric pressure ["low-pressure fuels"], such as petrol, diesel, Alcohols or the like.), at atmospheric pressure but gaseous is.

State of the art in the supply of low-pressure fuels is direct injection, in which fuel is injected at high pressure directly into the combustion chamber of the internal combustion engine, with stratified charge at partial load with spark-ignited fuels ("Innovations for safe, clean and economical driving [components, modules, systems ] ", Information brochure from Bosch with the number 1 987 485-ZVW2-0100-D, page 4 -8th). Their technology is known and is therefore not explained further here

With the previously known and on available on the market Feeding systems of LPG in the LPG squeezed into the combustion chamber of an internal combustion engine from the special, pressure-resistant liquid gas tank (blow-off pressure pressure safety valve: 30 bar) due to its own overpressure in an evaporator pressure regulator, where there is, by reducing the overpressure and with advancement of thermal energy to compensate for the evaporative cold, from the liquid in the gaseous Condition transferred and in this gaseous Physical state was supplied to the intake manifold of the engine, either inducted by the negative pressure of the combustion air flowing in the intake tract or by, via a own, additional Control unit controlled, active blowing in front of the intake valves the internal combustion engine.

The current state of the art in the supply of liquid gas represents the supply of the liquid gas into the intake tract in the liquid state, whereby a pump in conjunction with a pressure regulator is intended to ensure that the liquid gas reaches the injectors in the liquid phase by the pressure of the Liquid gas is constantly kept 2–3 bar higher than the liquid gas pressure in the tank. (http://www.gasautogasanlagen.de/Autogasanlagen/autogasanlage.html and http://www.autogastechnik.de/technik.html). ( EP 0 725 208 B1 . EP 0922851 A2 )

For the bivalent operation of internal combustion engines with spark-ignited low-pressure fuel in Combination with liquid gas have been for each fuel uses its own fuel delivery system. This has a relatively high construction cost.

Furthermore, the injection of LPG demonstrates the intake valves still to oust air sucked in by the evaporating fuel gas and thus for reduction available for combustion standing mixture mass.

Also with the injection of fuel upstream of the intake valves operation with stratified charge is not possible.

In the EP 0 725 208 B1 The configuration described for securing the liquid phase from liquid gas up to the injectors with pressure or temperature measurement in the liquid gas fuel tank has the disadvantage that it cannot ensure the desired function, since it does not take into account the heating of the liquid gas on its way into the injectors, which is particularly the case in close to the engine block in warm operating condition is considerable and cannot be cushioned in every operating condition by a pressure difference of 2-3 bar. Nor can a pressure of 22 bar be generated with a single electrically driven in-tank fuel pump of a conventional type, since the maximum operating pressures end at 6.5 bar.

Another disadvantage is that an additional electronic control unit the pressure fluctuations by variation the LPG injector opening times must compensate. In the case of bivalent operation, it must To do this, modify the signals of the electronic control of the gasoline injection system. If now the modifications of the additional electronic control unit is not also affected by the lambda probe, there are problems with exhaust gas cleaning.

Advantages of invention

• a) auch Flüssiggas direkt und flüssig in den Brennraum einer Brennkraftmaschine eingespritzt werden kann, wodurch es u.a.
• b) keinerlei Rückzündungsprobleme mehr gibt und daß,
• c) durch das Zusammenführen der Benzin- und Flüssiggaskraftstoffleitungen vor der Hochdruckpumpe des Einspritzsystems, mit einem Einspritzsystem und einer Einspritzregeleinheit wahlweise sowohl Niederdruckkraftstoffe (Benzin oder Diesel oder ähnliches), als auch Mitteldruckkraftstoff (Flüssiggas = Autogas = LPG = Liquified-Petroleum-Gas) oder ein Gemisch aus beidem direkt in den Brennraum einer Brennkraftmaschine eingespritzt werden kann.
• d) eine zusätzliche elektronische Kontrolleinheit, die Druckschwankungen des Flüssiggases durch Veränderung der Einspritzventilöffnungszeiten abfängt, überflüssig wird, da die Temperatur des Flüssiggases als beeinflussender Parameter durch die Hochdruckeinspritzung keine Rolle mehr spielt.
• e) durch den Wegfall der konkurrierenden zusätzlichen Einspritzregelung beim Betrieb mit Flüssiggas die Funiction der Lambda-Sonde auch in diesem Betriebsmodus uneingeschränkt erhalten bleibt. Das hat zur Folge, dass es keine Abgasprobleme gibt.
• f) durch die Messung der Flüssiggastemperatur am Hochdruckpumpeneingang statt im Tank der entscheidende Parameter gemessen wird, um den notwendigen Druck zu ermitteln, der das Flüssiggas in der Flüssigphase hält.

These problems are solved by the features listed in the claims, in that the present invention causes

• a) liquid gas can also be injected directly and liquid into the combustion chamber of an internal combustion engine, thereby making it, among other things
• b) there are no longer any reignition problems and that,
• c) by merging the gasoline and liquid gas fuel lines in front of the high-pressure pump of the injection system, with an injection system and an injection control unit, both low-pressure fuels (petrol or diesel or similar), as well as medium-pressure fuels (liquefied petroleum gas = LPG = liquefied petroleum gas) or a mixture of both directly in the combustion chamber of an internal combustion engine can be injected.
• d) an additional electronic control unit, which absorbs pressure fluctuations in the liquid gas by changing the injection valve opening times, becomes superfluous, since the temperature of the liquid gas no longer plays a role as an influencing parameter due to the high-pressure injection.
• e) the elimination of the competing additional injection control when operating with liquefied petroleum gas means that the lambda probe remains fully functional even in this operating mode. As a result, there are no exhaust gas problems.
• f) by measuring the liquid gas temperature at the high-pressure pump inlet instead of in the tank, the decisive parameter is measured in order to determine the necessary pressure that keeps the liquid gas in the liquid phase.

Further advantages of the invention:

• a) LPG is a product used in the processing of crude oil into fuels automatically arises. Its use increased thus the degree of utilization of the crude oil.
• b) opposite Direct fuel injection systems:
• 1. the higher Energy density (approx. 2%) of the LPG-air mixture increases performance
• 2. the higher Allow the octane number of LPG and the better internal mixture cooling a higher compression, which in turn, even at full load, the efficiency, the torque and increases performance.
• 3. Reduces the raw emissions of polluting pollutants itself, especially during a cold start, because the fuel-air mixture is enriched not necessary is.
• 4. CO2 emissions are reduced by up to 20%
• 5. because liquid gas contains almost no sulfur simplifies exhaust gas cleaning
• 6. Harmful toxic emissions of PAHs, aldehydes, benzene and toluene are reduced
• 7. no groundwater hazard by LPG as it is not water soluble is
• 8. The service life of the engine and spark plugs is extended by reducing aggressive acids and carbon deposits and less watering down of the lubricating oil
• c) Opposite LPG systems with manifold injection:
• 1. Reduced fuel consumption through direct injection. In the European Driving cycle (NEDC) the saving versus Motors with conventional Fuel supply method for liquid gas 15-20 %. Added to this is the fuel saving through the full filling of the Cylinder with combustion air, which in total saves fuel up to 30% possible are
• 2. There is no need for a second injection system and no additional control function for the medium pressure fuel as in EP 0 725 208 B1 described.

drawings

Embodiments of the invention are shown in simplified form in the drawings and in the following Description explained.

Show it 1 the system areas of direct fuel injection, 2 a monovalent version of the direct fuel injection system for the medium pressure fuel LPG in the variant with a low pressure regulator 6 and two fuel return lines 16 from the high pressure area, which feed the unused fuel back into the tank ( 4 ) 3 a monovalent version of the direct fuel injection system for the medium pressure fuel LPG in the variant with a fuel return line 19 ( 3 ) 4 a bivalent variant of 2 for medium and low pressure fuels. This variant is characterized by a low pressure regulator 6 and two fuel return lines 16 in the low pressure system that end in the low pressure fuel tank. 5 also shows a bivalent version, namely that of 3 , It differs in the arrangement of high pressure pump 5 and high pressure regulator 8th in the high pressure part of the in 4 shown variant. In addition, it has no separate low pressure regulator and only one fuel return line 16 whose low-pressure branch does not end in the low-pressure tank, but in the fuel supply line upstream of the high-pressure pump 20 empties.

description of the embodiments

The invention is based on internal combustion engines commercially available with a direct injection system for low-pressure fuels, which is usually fed from a low-pressure fuel tank with an in-tank pump as part of a fuel delivery module. For this reason, in 1 only the basic interaction, common to these internal combustion engines, of the system areas fuel supply A (here consisting of a medium pressure fuel supply A1 or a medium pressure fuel supply A1 and a low pressure fuel supply A2 including a switchover control E, which controls the switchover between the two fuels), high pressure part B, the electronic control C and the periphery D shown and dispensed with the further explanation of the areas B, C and D, because one of the advantages of here described invention it is that there is no need to intervene in these areas in order to inject liquid gas directly.

In 2 A monovalent version of the direct fuel injection system is shown, in which the low-pressure fuel system A2 is replaced by a medium-pressure fuel system A1. From a medium pressure resistant fuel tank 10 (Blow-off pressure 30 bar) is by the fuel pump 1 after opening the solenoid valve 3 LPG 18 into the supply line 12 pressed, flows through the fuel cooler 14 and then arrives at the inlet of the medium pressure fuel pump 4 , The fuel pump 4 if necessary, increases the pressure of the liquid gas again 18 and thus ensures together with the low pressure pressure regulator 6 making sure that the LPG 18 in liquid state to the inlet of the high pressure pump 5 arrives. In order for this to be guaranteed even during temperature peaks caused by heat conduction and heat radiation from the internal combustion engine to the high-pressure fuel pump close to the engine and also to the fuel lines, the vapor pressure of the LPG at the high-pressure pump inlet must always be lower than the total pressure of the fuel in the fuel circuit A. This can be caused by a second pressure stage in the low pressure pressure regulator 6 , the opening pressure of which is greater than the maximum evaporation pressure arising during operation or a variable change in the opening pressure controlled by a control unit 27 which processes the pressure or the temperature of the liquid gas as a control variable or by heating the LPG in the fuel tank 10 or cooling the liquid gas 14 can be achieved. Is shown in 2 the variant with an electric heating element placed in the fuel tank 23 as a heat source. The fuel heating is switched on by the control unit 27 if the difference in the temperature readings of the two temperature sensors 17 exceeds a predetermined setpoint, it is switched off when the temperature difference falls below another predetermined setpoint. In addition, the heating has 23 a temperature limit for safety reasons.

The high pressure pump 5 presses the liquefied petroleum gas, if necessary, with a pressure that has been changed from the fuel density factor (density of low pressure fuel to density of liquefied petroleum gas) and the air requirement factor via the injection valves into the combustion chamber of the internal combustion engine, regulated by the electronic control C. Unused, excess fuel is transferred via the return lines 16 and 19 in the liquid gas tank 10 recycled.

3 also shows a monovalent version of the liquid gas direct injection but with a different configuration of the high pressure part B. Here are rails 7 and high pressure regulator 8th connected with each other.

The 4 explains the hydraulic circuit diagram of a bivalent direct fuel injection system with a branch line 13 in the fuel supply line for supplying low-pressure fuel into the liquid gas tank 10 and two separate fuel return lines 16 to the fuel tank A medium pressure fuel system A1 with a supply line is shown 26 from the low-pressure fuel tank (not shown), in which, as usual, there is an in-tank pump as part of a fuel delivery module, which leads to a high-pressure fuel pump 5 leads. Via the fuel rail (common rail) 7 leads the high-pressure fuel line to the high-pressure fuel regulator 8th , Both from the high pressure regulator 8th as well as from the high pressure fuel pump 5 each has a fuel return line 16 back into the fuel tank.

To the low pressure fuel line 26 is the supply line for the LPG 12 connected that from the pressure tank 10 for the liquefied gas comes. Through solenoid valves 3 in combination with check valves 2 it is ensured that fuel from only one of the two fuel tanks to the high pressure pump 5 flows and the liquid gas with its higher pressure level does not press into the low-pressure fuel tank.

The second fuel pump 9 in this line is used for a brief pressure increase in the low-pressure fuel system in the phase of switching from the liquid gas mode to the low-pressure fuel mode. Without this second fuel pump 9 would after switching off the medium pressure fuel pump 4 the pressure level in the fuel supply lines 1 and 20 decrease to the pressure level of the low pressure circuit, i.e. below the pressure that prevents the liquefied gas from evaporating. However, there are liquid gas residues in the injection system at the time of switching and also for a while afterwards, which are prevented from evaporating by the increased pressure. The increased pressure is in the low pressure mode of operation by the second low pressure fuel pump 9 Maintained until all liquid gas in the entire pipeline system has been replaced by low-pressure fuel. The low pressure control valve 6 ensures constant pressure at the inlet of the high pressure fuel pump 5 , Analogous to 2 increases the fuel pump 4 the pressure of the liquid gas and thus forms the prerequisite for the liquid gas, even when heated, the HP pump 5 reached in the liquid state. Of the options described above to keep the liquefied gas liquid in 4 the variants of fuel cooling and temperature-controlled pressure increase are shown.

A fuel cooler is used in the variant with cooling of the liquid gas 14 that in front of the fuel pump 4 is appropriate, the desired purpose. Exceeds the fuel temperature difference between the fuel tank 10 and high pressure pump inlet 5 a critical value (approx. 30 ° C), then the temperature sensor 17 the cooling process started, where cooling by an evaporating Medium, either through the refrigerant in the cooling circuit of the air conditioning system or through a branch of part of the liquid gas 18 is effected. The version with branched liquid gas is shown 18 , Through the temperature sensor 17 becomes the solenoid valve 21 switched that the LPG the way to the throttle 24 of the fuel cooler 14 releases where it evaporates and cools the fuel through its evaporative cooling. The gaseous fuel is then fed to the intake manifold of the engine via the vaporized fuel circuit.

The temperature-controlled pressure increase is achieved here by a pump controlled by the liquid gas temperature 28 causes the compensation chamber of the pressure regulator, which is sealed with a membrane to the pressure chamber 6 pressurized, which adds to the spring pressure of the compression spring. The pressure in the compensation chamber rises analogously to the temperature of the liquefied gas and thereby increases the necessary opening pressure for the liquefied gas.

The additional fuel pump 9 also opens up the possibility of a further branch line 13 that in the return line for the LPG 16 opens and together with this into the filling line 11 for the liquefied petroleum gas, pumping low-pressure fuel into the liquefied petroleum gas tank, whereby a low-pressure fuel-liquefied gas mixture with freely selectable mixture proportions can be generated. This process is controlled by a separately switchable solenoid valve 15 , By adding low pressure fuel to the LPG, lubrication problems in the system are avoided.

From the fuel supply line 20 branches in front of the high pressure pump 5 a control line 22 from the control piston of the high pressure regulator 8th when operating with liquefied petroleum gas, a pressure is added which adds to a spring tension and, if necessary, thereby generates the necessary higher injection pressure in liquefied petroleum gas mode.

In liquefied petroleum gas operating mode, the excess liquefied gas that is conveyed beyond the engine's requirements is fed via the return line for the medium-pressure fuel 19 into the LPG fill line 11 from there and returns to the LPG tank 10 , check valves 2 prevent the liquid gas from escaping 18 ,

The invention has advantages in several Levels. Because the LPG now direct and fluid is injected into the combustion chamber, it no longer displaces intake air. This increases the degree of filling of the Cylinder opposite Injection in the intake tract and thus the performance of the Engine. At the same time, all the advantages of the direct injection process remain receive. The second level of advantage is the structural simplification with the liquefied gas system. The gas-air mixer, the evaporator pressure regulator, the fuel pump and injectors for the LPG fall away.

The third level of benefit is control simplification. Because the existing control system for the Low pressure fuel for Both types of fuel can be used is its own measuring and control system for the LPG not necessary and therefore there are no competing control variables, the influence on take the fuel mass metering.

5 also shows a bivalent version of the direct fuel injection but with a different configuration of the high pressure part B. Here are rails 7 and high pressure regulator 8th connected with each other. The excess fuel is in low pressure mode via the fuel return line 16 before the high pressure pump 5 back into the feed line 20 returned, but in the medium pressure mode in the liquid gas tank 10 ,

A fuel tank for LPG is shown 10 from which a fuel line 12 leads away and a direct injection system B, consisting of a high pressure pump 5 , a manifold 7 with high pressure lines leading to high pressure injectors 21 and a pressure control valve 8th , from which a fuel return line 16 before the high pressure pump 5 into the common fuel supply line 20 empties. The functionality of the modules otherwise corresponds to 4 ,

1

Fuel pump the medium pressure fuel supply (LPG system)

2

check valve

3

magnetic valve

4

Fuel pump the medium pressure fuel supply (LPG system)

5

high pressure pump

6

Low-pressure regulator

7

Fuel rail (Common rail)

8th

High pressure regulator

9

Second Low pressure fuel supply fuel pump

10

flameproof Tank for medium pressure fuel (LPG)

11

filling line the medium pressure fuel supply

12

supply for the Medium-pressure fuel

13

Short line

14

Fuel cooler

15

magnetic valve in the short-circuit line

16

return for the Low pressure fuel

17

temperature sensor

18

LPG (LPG)

19

return for the Medium-pressure fuel

20

common Fuel line

21

magnetic valve for the Coolant supply

22

control line

23

Heating fuel

24

throttle

25

probe

26

Low-pressure fuel line

(of the fuel pump in the low pressure fuel tank)

27

control unit to increase pressure in LPG mode

28

pump

Claims (16)

Direct fuel injection system for internal combustion engines with a fuel supply A, consisting either of a medium-pressure fuel supply A1 (PN = 25 bar), including a medium-pressure-resistant fuel tank (blow-off pressure of the safety valve = 30 bar), or of a medium-pressure fuel supply A1 and a low-pressure fuel supply A2 (PN = 3–4 bar), a high-pressure part B, an electronic control unit C, and periphery D (e.g. turbocharger or exhaust gas recirculation), characterized in that the medium-pressure fuel supply A1 or the medium-pressure fuel supply A1 and the low-pressure fuel supply A2 from the coupling point of the medium-pressure part A1 and the low-pressure part A2 by means of suitable connection systems medium-pressure resistant ( PN = 25 bar) are designed, e.g. B. by cutting ring screw connection of the fuel line connections and medium pressure resistant fuel hoses with medium pressure resistant pressed screw connections or other suitable medium pressure resistant connection systems. Direct fuel injection system according to claim 1, characterized in that liquefied gas 18 , also referred to as LPG (LPG = liquefied petroleum gas = propane-butane gas mixture with different percentages, hereinafter referred to as medium-pressure fuel), is injected directly into the combustion chamber of the internal combustion engine in the liquid state. Fuel direct injection system. according to claim 2, characterized in that the fuel supply of the medium pressure part A1 by two or more fuel pumps connected in series 1 . 4 is able to generate a pressure that, at all in operation at the inlet to the high pressure pump 5 occurring fuel temperatures, is above the evaporation pressure of the liquid gas, the fuel pump 1 in the pressure-resistant liquid gas tank 10 (Blow-off pressure 30 bar) is placed. Fuel direct injection system according to claim 3, characterized in that in a system with a fuel low pressure regulator 6 this directly at the entrance to the high pressure pump 5 is placed for the fuel circuit A, and its opening pressure is either set constant or has two opening pressure levels, one for the gasoline and one for the liquid gas or can be influenced via a control, the determining control variable being the temperature-dependent vapor pressure curve of the liquid gas, measured at the entrance to the High pressure pump. Direct fuel injection system according to one of the preceding claims, characterized in that the fuel before entering the high pressure part B by one or more cooling devices 14 can be cooled. Direct fuel injection system according to claim 5, characterized in that the fuel temperature can be regulated by cooling. Direct fuel injection system according to claim 6, characterized in that the cooling device 14 is cooled by branched, evaporating liquefied gas. Direct fuel injection system according to one of the preceding claims, characterized in that the liquid gas tank 10 can be heated, e.g. B. by one in the tank 10 attached electric heating element 23 or electrically heated heating mats around the tank or through branched cooling liquid or through the heat radiation of the exhaust pipe or other suitable means. Direct fuel injection system according to one of the The aforementioned claims, characterized in that the liquid gas tank is thermally insulated. Direct fuel injection system according to one of the preceding claims, characterized in that additionally a low-pressure fuel supply A2 including low-pressure fuel tank and fuel pump, in front of the high-pressure part B so connected to the fuel lines of the medium-pressure system A1 and by, controlled by a control logic E, valves 3 is alternately opened or locked so that with only one injection system B and the associated injection control C, both liquid gas (medium pressure fuel) and, alternatively, spark ignition fuels that are liquid at atmospheric pressure and room temperature (low pressure fuels) are directly and liquid injected into the combustion chamber of the internal combustion engine can be. (Bivalent direct fuel injection system) Direct fuel injection system according to claim 10, characterized in that the low-pressure fuel supply A2 and the medium-pressure fuel supply A1 by switchable valves 3 and check valves 2 are locked against each other by the control logic E such that the low pressure fuel tank is not subjected to the higher pressure of the medium pressure fuel system A1. Direct fuel injection system according to claim 11, characterized in that, to compensate for the different parameters of the different fuels, in particular fuel density or air requirement number, by the high pressure pump 5 generated injection pressures, controlled by the high pressure control valve 8th , these fuel parameters can be changed accordingly if these different parameters exceed the control range of the lambda sensor of the injection control. Direct fuel injection system according to claim 12, characterized in that at Switch from operation in medium pressure mode to low pressure mode the control logic E the pressure in the components through which both fuels flow in the fuel circuit A for so long at the level of the medium pressure fuel circuit A1 holds until the low-pressure fuel has completely displaced the medium-pressure fuel there. Direct fuel injection system according to claim 13, characterized in that a measuring device 25 When changing the fuel type, a control signal is generated which opens the valves 3 in the return lines 16 to the low pressure tank and the return of the fuel pump output in the low pressure fuel system to the level required for this system at this time, e.g. B. by switching off the additional fuel pump 9 the low pressure fuel supply A2. Direct fuel injection system according to one of the aforementioned Expectations characterized in that fuel pumps that are used to supply the Internal combustion engine with fuel are currently not required z. B. because the necessary system pressure is generated by a single pump can be switched off by the control logic E, the determining control variable again the vapor pressure curve of the liquefied gas is. Direct fuel injection system according to one of the preceding claims, characterized in that from the fuel inlet of the low pressure system A2 upstream of the high pressure pump 5 a fuel line 13 branches off to the return line for the medium pressure fuel 19 is coupled pressure-tight and through a valve 15 can be opened and closed, which makes it possible to add low pressure fuel to the liquid gas.